The following discussion of the background to the invention is intended to facilitate an understanding of the present invention. However, it should be appreciated that the discussion is not an acknowledgment or admission that any of the material referred to was published, known or part of the common general knowledge in any jurisdiction as at the priority date of the application.
Post-tensioning (“PT”) is a technique used in the construction of buildings, particularly those where the floors of the building are intended to have long spans uninterrupted by vertical pillars. PT involves reinforcing (strengthening) concrete or other materials with high strength steel strands or bars. These strands and bars are generally referred to as tendons.
The problem with this approach is that it is generally not possible to pour an entire floor as a single floor plate due to size restriction, continuity requirements and/or restraint conditions. As a consequence, the floor is commonly formed in sections or individual slabs. These sections or slabs are commonly poured at different time to each other. To ensure that the floor is more or less continuous, each section or slab contains suitable tendons such as PT wire cables or PT strand cables.
As each section or slab cures and settles, the sections or slabs may move relative to each other. This means that the joint connecting the sections or slabs must be capable of accommodating this relative movement. At the same time, the joint operates to allow temporary release of restraining effects of the various sections relative to one another and thus ensure that the maximum amount of PT pre-compression force is transferred into the floor plates. If insufficient PT pre-compression force is transferred into the floor plates there exists the possibility of cracking within the sections or slabs—thereby reducing the longevity and the integrity of the resulting floor plate.
One past method of allowing for such movement and transfer of pre-compression force has been to place temporary movement joints at strategic locations within the building. Each temporary movement joint allows for movement during curing and settling of the structural elements that it joins. Once the joined structural elements have cured and settled, the temporary movement joint is permanently locked so as to provide a more or less continuous floor or other element of the building.
While this approach works, almost all temporary movement joints of the prior art suffer from one or more of the following problems:                If the surfaces that the temporary movement joints seek to connect move relative to each other during settling, an air gap may be formed which leaves both the temporary movement joint and at least part of the tendon exposed to the atmosphere and thus subject to corrosion and the like until sealed.        There is significant difficulty in sealing the temporary movement joint—in particular the underside of the temporary movement joint.        
A consequence of the first problem is that prior art temporary movement joints must be made from corrosion resistant materials, such as stainless steel. When combined with the fact that the materials must also be fire resistant or incorporate other attributes to meet building regulations, the cost of manufacturing such temporary movement joints may be up to ten times higher than the cost of manufacturing from less exotic materials.
The second problem presents a situation where the temporary movement joint is not adequately strengthened or that sealant may be lost from the joint. In both cases, a workman is then required to caulk the temporary movement joint at a later date and thus ensure that the temporary movement joint is properly sealed and thus locked in place. This requirement for remedial action is time-consuming and expensive in addition to delaying completion of the building. It is therefore an object of the present invention to provide a connector for use in forming joints that ameliorates, at least in part, one or more of the aforementioned problems.